IIRC, member kenworth Goose moved the leafs to the inside frame rails by boxing the frame and moving the mounts left to right on inside of frame rails. then narrowed a 8 1/4 rear axle for 18.5 or 21.5 M/Ts

I didn't get any of those pics. but it was a cool way of narrowing the 8 1/4 housing at home with some all thred rod and torch/welder.

a few here said he could not do it...but he did. AND it worked! IIRC even Moser looked at it when they cut/resplined the stock axles and said well done.